The present invention relates to liquid energy sources and in particular liquid energy sources comprising a liquid fuel and lipid vesicles containing a fuel additive such as water, which have enhanced performance characteristics compared to conventional gasoline and diesel fuels.
One recurring problem with existing commercial fuel is incomplete combustion, which results in higher emissions of nitrous oxide, carbon monoxide, hydrocarbons, and sulfur dioxide. It has previously been demonstrated that inclusion of up to 3% water in the fuel system reduces emissions of these gases and increases the octane rating.
One major problem with adding water and other aqueous components directly to liquid energy source, however, is that while the liquid energy source is capable of dispersing a limited amount of water, if too much water is present the water will separate out, along with other water soluble components of the liquid energy source. The separated water may cause damage to the engine and fuel systems by rusting and corroding metal parts.
In view of the problems of the current art, improved methods for incorporating water and other fuel additives in liquid energy source have been desired, as well as new liquid energy source compositions having the desired properties.
The present invention relates to liquid energy sources comprising a liquid fuel and lipid vesicles containing a fuel additive such as water, which have enhanced performance characteristics compared to conventional gasoline and diesel fuels. The present invention may be used to enhance the performance characteristics of conventional gasoline and diesel fuels, by reducing emissions of pollutants and increasing the octane rating.
The present invention features a liquid energy source containing a liquid fuel and lipid vesicles having at least one lipid bilayer formed from at least one wall former material, and which have at least one cavity containing a fuel additive. The fuel additive-containing lipid vesicles allow incorporation of fuel additives such as water or hydrazine in liquid energy sources more effectively and precisely than previously attainable. In an advantageous embodiment, the liquid energy source may also contain a polymeric dispersion assistant, which reduces the interfacial tension and coalescence of vesicles during dispersion process and storage, and thereby provide transparent looks to the liquid energy source. As such, in a preferred version of this embodiment, the addition of the polymer results in a transparent fuel. The polymer may be a polyoxyethylene glycol diester of polyhydroxy fatty acids represented generally by the following formula: 
wherein RCO is a moiety derived from a polyhydroxy fatty acid and the value of n generally ranges between approximately 15 to approximately 40. In another embodiment the polymer is a polyoxyethylene glycol diester of fatty acids represented by the following general formula: 
wherein RCO is a moiety derived from fatty acids such as, for example, stearic, palmitic, oleic, and lauric acids and n generally ranges between approximately 15 to approximately 40. In yet another embodiment, the polymer is a polyoxyethylene-polyoxypropylene block polymer represented by the following formula: 
where the average value of x and the average value of z are each independently between about 2 and about 21 and the average value of y is between about 16 and about 67.
In another embodiment, the lipid vesicles have a cavity containing a fuel additive. The lipid vesicles may be paucilamellar, e.g., having 2-10 lipid bilayers surrounding an amorphous central cavity.
In yet another embodiment, the lipid vesicles are present in the liquid fuel in an amount sufficient to provide a concentration of the fuel additive (e.g., water) from about 0.01% to about 10%.
In a preferred embodiment, the liquid fuel is suitable for use in an internal combustion engine, e.g. gasoline or diesel fuel.
The invention also features a method for improving the efficiency of an internal combustion engine, by fueling the internal combustion engine with a liquid energy source containing a liquid fuel and lipid vesicles having at least one lipid bilayer formed from at least one wall former material and a at least one cavity containing a fuel additive. The liquid energy source may also desirably contain a polymeric dispersion assistant.
In another aspect, the invention features a method of reducing emissions from an internal combustion engine, by fueling said internal combustion engine with a liquid energy source comprising a liquid fuel and lipid vesicles comprising at least one lipid bilayer formed from at least one wall former material and a central cavity containing a fuel additive. The liquid energy source preferably also contains a polymeric dispersion assistant.
The present invention relates to liquid energy sources comprising a liquid fuel and lipid vesicles containing a fuel additive such as water, which have enhanced performance characteristics compared to conventional gasoline and diesel fuels. The present invention may be used to enhance the performance characteristics of conventional gasoline and diesel fuels, e.g., by reducing emissions of pollutants and increasing the octane rating.
The present invention features a liquid energy source containing a liquid fuel and lipid vesicles which are comprised of at least one lipid bilayer formed from at least one wall former material.
The term xe2x80x9cliquid fuelxe2x80x9d includes fuels such as gasoline, diesel fuels, alternative fuels, bio-diesel, engineered fuels, kerosene, jet aviation fuels or mixtures thereof. In a preferred embodiment, the liquid energy source is suitable for an internal combustion engine.
The term xe2x80x9cwall former materialxe2x80x9d includes lipids and sterols. Preferred wall former materials include non-ionic amphiphiles. In a preferred embodiment, the lipid bilayer is formed from at least a primary wall former. In an embodiment, the primary wall former is a non-ionic amphiphile. However, vesicles can be formed by blending these amphiphile with other amphiphile, which may or may not form vesicles or a lamellar phase on its own. Preferred other amphiphiles have like chain length and unsaturation but some variations are acceptable. The term xe2x80x9clike chain length and unsaturationxe2x80x9d, as used herein, means and implies that both materials would have identical fatty add chains.
The wall former material present in the lipid bilayer(s), is desirably a non-ionic amphiphile, e.g., C,12-C18 fatty alcohols, polyoxyethylene acyl alcohols, block copolymers, polyglycerols, sorbitan fatty acid esters, ethoxylated Cl12-Cl18 glyceryl mono- and diesters, propylene glycol stearate, sucrose distearate, glyceryl dilaurate, glucosides, and mixtures thereof.
Inclusion of sterols in the construction of the vesicles of the present invention is believed to help buffer the thermotropic phase transition of the membrane layer, i.e., it enables the lipid membrane structure to be less susceptible to temperature changes in the region of the transition temperature. The sterols also insure optimal vesicle size and increase bilayer stability. Sterols include any sterol known in the art to be useful as modulators of lipid membranes. Suitable sterols include but are not limited to cholesterol, cholesterol derivatives, hydrocortisone, phytosterol, or mixtures thereof. In one embodiment, the sterol is phytosterol supplied from avocado oil unsaponifiables. The use of this sterol, in particular, to form lipid vesicles is described in U.S. application Ser. No. 08/345,223, entitled Lipid Vesicles Containing Avocado Oil Unsaponifiables, the contents of which are incorporated by reference herein.
In furher embodiment, the lipid bilayers may also contain a secondary wall former. The secondary wall former is preferably selected from the group consisting of quaternary dimethyl diacyl amines, polyoxyethylene acyl alcohols, sorbitan fatty acid esters and ethoxy sorbitan fatty acid esters.
In a further embodiment, the lipid bilayers may also contain a charge producing agent, e.g., dimethylstearyl amine, dicetyl phosphate, cetyl sulfate, phosphatidic acid, phosphatidyl serine, oleic acid, palmitic acid, stearylamines, oleylamines, and mixtures thereof.
In a particularly advantageous embodiment, the fuel additive and/or liquid energy source may contain a polymeric dispersion assistant. Often when a fuel additive is combined with the fuel, a cloudy mixture results, which is aesthetically undesirable and may lead the vendor or customer to conclude that the fuel is adulterated or spoiled. The liquid energy source containing the polymeric dispersion assistant is transparent. In one embodiment, the polymeric dispersion assistant may be a polyoxyethylene-polyoxypropylene glycol block polymer of the following formula: 
where the values of x, y, and z are each independently integers between about 1 and about 100. Preferably, the average value of x and the average value of z are each independently between about 2 and about 21 and the average value of y is between about 16 and about 67. In one advantageous embodiment, the average value of x and the average value of z are each independently about 3, and the average value of y is about 30. In another advantageous embodiment, the average value of x and the average value of z are each independently about 6, and the average value of y is about 39. In yet another advantageous embodiment, the average value of x and the average value of z are each independently about 7, and the average value of y is about 54.
In another embodiment, the polymeric dispersion assistant is a polyoxyethylene glycol diester of polyhydroxy fatty acids which can be represented generally by the following formula: 
where RCO is a moiety derived from a polyhydroxy fatty acid and the value of n generally ranges between approximately 15 to approximately 40. Preferred examples of such moieties include, for example, PEG30 dipolyhydroxystearate.
In another embodiment the polymeric dispersion assistant is a polyoxyethylene glycol diester of fatty acids represented by the following general formula: 
where RCO is a moiety derived from fatty acids such as, for example, stearic, palmitic, oleic, and lauric acids and n generally ranges between approximately 15 to approximately 40.
In a preferred embodiment, the lipid vesicles are paucilamellar lipid vesicles which are generally characterized as having two to ten lipid bilayers or shells with small aqueous volumes separating each substantially spherical lipid shell. Generally, the innermost lipid bilayer surrounds a large, substantially amorphous central cavity which may be filled with either an aqueous solution or other fuel additive such as noted herein. Alternatively, when the lipid vesicles are paucilamellar, multiple additives may be enclosed in each lipid bilayer shell so as to provide a blend of additives in the vesicle, e.g., a vesicle could comprise both water and kerosene, thus providing a more versatile fuel additive.
In one embodiment, the lipid vesicles are present in the liquid fuel in an amount sufficient to provide a concentration of the fuel additive in the range of from 0.01% to 10% of the fuel. In one particularly advantageous embodiment, the lipid vesicles are present in the liquid fuel (e.g., gasoline or diesel fuel) in an amount sufficient to provide a concentration of water in the liquid fuel of 5% or less, preferably 1.7% , and more preferably 3%.
The term xe2x80x9cfuel additivexe2x80x9d is art recognized and is intended to include compounds such as water, ethanol, hydrazine, hydrogen peroxide, and methyl isobutane ketone, soya methyl ester and mixtures thereof. In a particularly preferred embodiment, the fuel additive is water.
The invention also features a method of improving the efficiency of an internal combustion engine, by fueling the internal combustion engine with a liquid energy source containing a liquid fuel and lipid vesicles which have at least one lipid bilayer formed from at least one wall former material and a cavity containing a fuel additive.
In addition, the invention features a method of reducing emissions from an internal combustion engine, by fueling the internal combustion engine with a liquid energy source containing a liquid fuel and lipid vesicles which have at least one lipid bilayer formed from at least one wall former material and a cavity containing a fuel additive.
Aqueous filled vesicles, e.g., vesicles having their amorphous central cavities filled with a water-miscible solution, may be formed using either the xe2x80x9chot loadingxe2x80x9d technique disclosed in U.S. Pat. No. 4,911,928 or the xe2x80x9ccold loadingxe2x80x9d technique described in U.S. Pat. No.5,160,669, the disclosures of which are incorporated herein by reference. In either case, a lipid phase is formed by blending a primary wall former and compatible amphiphile(s),with or without sterols or lipophilic materials to be incorporated into the lipid bilayers, to form a homogenous lipid phase. In the xe2x80x9chot loadingxe2x80x9d technique, a lipophilic phase is made and heated, and is blended with a heated aqueous phase (e.g., water, saline, or any other aqueous solution which will be used to hydrate the lipids) under shear mixing conditions to form the vesicles. xe2x80x9cShear mixing conditionsxe2x80x9d, as used herein, means a shear equivalent to a relative flow of 5-50 m/s through a 1 mm orifice. The paucilamellar lipid vesicles of the disclosure can be made by a variety of devices which provides sufficiently high shear for shear mixing. A device which is particularly useful for making the lipid vesicles of the present invention is described in U.S. Pat. No. 4,985,452, assigned to Micro Vesicular. Systems, Inc.
In the xe2x80x9ccold loadingxe2x80x9d technique, the lipid phase and the aqueous phase are blended under shear mixing conditions to form vesicles. Once the substantially aqueous filled lipid vesicles are formed, they are combined with the xe2x80x9ccargoxe2x80x9d material to be encapsulated, e.g., the water immiscible material. Droplets of the water immiscible material enter the vesicles, presumably by a process resembling endocytosis. The cold loading method has been described in more detail in the aforementioned U.S. Pat. No. 5,160,669. These vesicles are then blended under low shear conditions, as described in U.S. Pat. No. 5,160,669.
Once the vesicles are formed, they are diluted with additional liquid energy source. If a polymer additive is also used, the polymer is added at this time. It is occasionally necessary to melt the polymer before incorporating it into the liquid energy source mixture.